Drag Reducing Device

ABSTRACT

A drag reducing device includes an air flow turning component having a curved surface adapted to turn air flow passing over the curved surface, a first mounting component for connecting the air flow turning component to a rear door of the vehicle, and a second mounting component for connecting the air flow turning component to one of the opposite side walls of the vehicle. The mounting components are configured so that the air flow component is automatically in a deployed position when the rear door is closed, so the air flow turning component turns air flow passing along the side the vehicle inward to thereby reduce drag. The mounting components are further configured so that the air flow component is automatically stowed between the rear door and the vehicle side wall when the door is fully opened. The air turning component is sized for a minimal prominence when stowed.

REFERENCE TO RELATED APPLICATION

The application claims priority to and is a utility conversion ofco-pending provisional application Ser. No. 61/538,391, filed on Sep.23, 2011, the entire disclosure of which is incorporated herein byreference.

BACKGROUND

The present disclosure relates to drag reduction devices for landvehicles, such as trucks, tractor-trailer rigs, vans, buses,recreational vehicles and similar vehicles having a large frontal area.

Fuel economy is a persistent concern for all land vehicles and isparticularly acute for large vehicles such as trucks and tractor-trailerrigs. Fuel economy improvements have been achieved by innovation inengine design and improvements in fuel composition. However, the sizeand shape of the vehicles plays a substantial role in fuel economy.Ultimately, drag is the greatest enemy to fuel economy, with as much as70% of the engine power devoted to cutting through the air in front ofthe vehicle.

Drag is a force that resists the movement of a body through a fluid,whether the body is a baseball and the fluid is air, or the body is aswimmer moving through water. Drag is a function of twocomponents—friction drag and pressure drag. Friction drag is a forcethat acts tangential to a surface of the body. Friction drag isincreased by irregularities or roughness on the surface and decreased bymaking the surface more slippery. A clean truck cuts through the airmore efficiently and with less friction drag than a dirty truck.

Pressure drag is a force that acts perpendicular to a surface and is afunction of the surface area in the direction of travel as well as thevelocity or speed at which the body is traveling. Pressure dragincreases as the square of velocity so that doubling vehicle speedactually creates four times more pressure drag. On the other hand,pressure drag is directly related to surface area so that a ten percentreduction in surface area leads to a ten percent decrease in pressuredrag.

For aerodynamically configured vehicles, such as airplanes, frictiondrag contributes more heavily to overall drag than pressure drag.However, for land vehicles this relationship is reversed significantly.For a typical tractor-trailer, pressure drag can be as much as ten timesgreater than friction drag due to the large frontal surface area of thetruck. Unfortunately, the size of these types of vehicles is dictated bytheir function—hauling products or materials. Unlike passenger vehicles,the box-like shape of trucks cannot be significantly altered. A smallerfrontal surface area means a smaller truck, which means less cargo thatcan be hauled. Pressure drag in land vehicles, and especially in trucks,is increased by pressure “hot spots”, such beneath the undercarriage,behind the rear of the trailer or between the tractor and the trailer.These hot spots are generally regions of low pressure, which causes airflowing over the vehicle to deviate from a streamlined path around thevehicle. Vortices can form in these hot spots that significantlyincrease the pressure drag.

In quantitative terms, if a square body has a drag coefficient (C_(D))of 1.00, elongating the body into a rectangular shape reduces C_(D) to0.80. Adding a rounded nose cuts the coefficient in half to 0.40. Addinga “boat tail” or a conical tail decreases C_(D) further to 0.20. Thetypical boattail configuration includes plates projecting from the rearof the vehicle and angled inwardly at an angle of 10-15°. An ellipticalbody tapered at both ends produces a drag coefficient less than 0.05,but the shape significantly reduces available cargo space and isdifficult to produce.

It has been estimated that a 20% reduction in drag yields at least a 10%increase in fuel economy at highway speeds. For truckers and truckingcompanies, this increase in fuel economy means significantly reducedfuel costs year in and year out. For the environment, increases in fueleconomy mean fewer deleterious emissions. A significant amount of efforthas been expended in developing drag reduction technology for trucks.These efforts include streamlining the tractor, introducing seals, airdeflectors or vortex generators in the gap between the tractor andtrailer, and adding undercarriage skirts, guide vanes, air deflectorsand boat tails to the trailer. Each of these modifications contributesin some measure to the overall drag reduction, so a fully optimized rigwill incorporate a number of these improvements.

Presently, the typical drag reduction device utilizes “mechanical”redirection of the air flow to reduce drag. For instance, one type ofdevice utilizes spoilers or fairings mounted to the top trailing edge ofa vehicle or trailer to redirect the airflow and attempt to reduceturbulence. Another drag reduction device is the boat tail device thatincludes boat tail plates extending rearward from the rear of thetrailer. Boat tail devices can reduce drag by up to ten percent. Thetypical boat tail is a large shell that is mounted over the rear doorsof the trailer. Such devices are cumbersome to install and remove.Moreover, the large unitary shell is difficult to store when access tothe rear doors is desired, such as to unload the trailer.

Other “mechanical” drag reduction devices require intervention by thevehicle operator to deploy and stow the device, while still othermechanical approaches require the vehicle operator to manipulate thedrag reduction device to access the rear doors of the vehicle ortrailer. Some mechanical devices are mounted directly to thevehicle/trailer doors which can eliminate the need to manipulate thedevice in order to access the trailer door. However, these devices arebulky and prevent the trailer/vehicle door from being fully opened flatagainst the side wall of the trailer/vehicle. This discrepancy can posesignificant risks at shipping/receiving locations where trucks arebacked in to closely spaced loading docks. A door that projects too faraway from the side of the trailer can be struck by an adjacent vehicleas it attempts to back into an adjacent loading dock.

A more recent development in drag reduction are non-mechanical devices,meaning devices that do not mechanically turn or redirect the air flow,like a spoiler, but instead generate a force that acts on the air flow.One such device is a plasma flow actuator that provides a “body force”to the air flow as it passes over a surface to accelerate the air,thereby stabilizing the boundary layer and causing the air to remain“attached” or conform to the surface to reduce or eliminate flowseparation, turbulence and, ultimately, drag. One type of plasma flowactuator is electronically controlled for activation at appropriatevehicle speeds and for precise operation to optimize the drag reducingeffect.

Whether the actuator is mechanical or non-mechanical, there is apersistent need for a drag reduction device that does not impede theability to open the rear doors of a trailer or truck on which the deviceis mounted. Moreover, in order to ensure that the drag reduction deviceis consistently used, the device should be “automatic”, meaning that itdoes not require any intervention by the vehicle operator to deploy orto position the device clear of the vehicle/trailer doors when access isdesired for loading or unloading the vehicle. There is also a need for adrag reduction device that has a lower profile than existingdevices—i.e., that does not extend excessively beyond the end of thevehicle—to lessen the chance for damaging contact when the vehicle ismoved in reverse.

DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of the rear of a vehicle or trailer with adrag reduction device mounted thereon.

FIG. 2 is a perspective view of the device shown in FIG. 1, depictedwith the rear door of the vehicle or trailer partially opened.

FIG. 3 is a top view of the device shown in FIG. 2 with rear doorpartially open.

FIG. 4 is a top view of a hinge component of the device depicted in FIG.3.

FIG. 5 is a top view of the drag reduction device depicted in FIG. 3,shown with the rear door opened further.

FIG. 6 is a top view of the drag reduction device depicted in FIG. 3,shown with the rear door fully open and the drag reducing device in itsfully stowed position.

FIG. 7 is a top view of the drag reduction device depicted in FIG. 6,shown with the rear door fully closed and the drag reducing device inits deployed position.

FIG. 8 is a rear perspective view of a drag reduction device accordingto a further embodiment, shown with the device in its deployed position.

FIG. 9 is top view of a drag reduction device shown in FIG. 8 with thedevice in its deployed position.

FIG. 10 is top view of a drag reduction device shown in FIG. 8 with thedevice in its stowed position.

FIG. 11 is a top perspective view of a drag reduction device accordingto a further embodiment in its deployed position.

FIG. 12 is a top view of the drag reduction device shown in FIG. 11.

FIG. 13 is a top view of the drag reduction device depicted in FIG. 11,shown with the device in its stowed position.

FIG. 14 is a top perspective view of a drag reduction device accordingto a further embodiment, shown with the device in its deployed position.

FIG. 15 is a top view of the device shown in FIG. 14.

FIG. 16 is an enlarged top view of an attachment element for use withthe device shown in FIG. 15.

FIG. 17 is a top view of a drag reduction device according to yetanother embodiment with the device in its deployed position.

FIG. 18 is a top view of the drag reduction device shown in FIG. 17,with the rear door partially opened.

FIG. 19 is a top view of the device shown in FIG. 17, with the device inits stowed position.

FIG. 20 is a perspective view of the rear of the vehicle or trailerhaving a sliding cover system with a drag reduction device according toan additional embodiment.

FIG. 21 is a top view of the drag reducing device of FIG. 20 shown inits stowed position.

FIG. 22 is an enlarged view of a tension element used with the dragreducing device shown in FIG. 20.

FIG. 23 is a bottom perspective view of a locking mechanism for a dragreducing device of another embodiment, shown with the locking mechanismin its latched position.

FIG. 24 is a rear perspective view of lower portion of the lockingmechanism shown in

FIG. 23.

FIG. 25 is a rear perspective view of the upper portion of the lockingmechanism illustrated in FIG. 23, shown with the locking mechanism inits unlatched position.

FIG. 26 is a rear perspective of the lower portion of the lockingmechanism shown in FIG. 25.

FIG. 27 is a rear perspective view of a locking mechanism according to afurther embodiment for use with the sliding cover system of FIG. 20,with the mechanism shown in the locked position and the drag reducingdevice in its deployed position.

FIG. 28 is a rear perspective view of the locking mechanism shown inFIG. 27, with the mechanism moving from its locked to its unlockedposition.

FIG. 29 is a rear perspective view of the locking mechanism shown inFIG. 28, with the mechanism in its unlocked position and the dragreducing device in its stowed position.

FIG. 30 is a top view of a side drag reducing device for use with asliding cover system according to a further embodiment, with the deviceshown in its deployed position.

FIG. 31 is a top view of the side drag reducing device of FIG. 30 withthe device shown in its stowed position.

FIG. 32 is a rear perspective view of a top drag reducing device shownin its deployed position.

FIG. 33 is rear view of the top drag reducing device of FIG. 32 shown inits stowed position.

FIG. 34 is a top view of the top drag reducing device of FIG. 33 as wellas a side drag reducing device, both in their stowed positions.

FIG. 35 is a bottom perspective view of a top drag reducing deviceaccording to another embodiment.

FIG. 36 is a rear perspective view of a top drag reducing deviceaccording to a further embodiment shown in its deployed position.

FIG. 37 is a top view of the top drag reducing device shown in FIG. 36.

FIG. 38 is a perspective view of the top drag reducing device shown inFIG. 36 with the device in its stowed position.

FIG. 39 is a side view of an extrusion for a top drag reducing deviceaccording to yet another embodiment.

FIG. 40 is a rear perspective view of top and side drag reducing devicesmounted on a vehicle having a roll-up rear door.

FIG. 41 is an enlarged view of the drag reducing devices illustrated inFIG. 40, shown with the devices in their stowed positions.

FIG. 42 is an enlarged perspective view of the drag reducing devicesillustrated in FIG. 40, shown with the devices in their deployedpositions.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and described in the following written specification. It isunderstood that no limitation to the scope of the invention is therebyintended. It is further understood that the present invention includesany alterations and modifications to the illustrated embodiments andincludes further applications of the principles of the invention aswould normally occur to one skilled in the art to which this inventionpertains.

According to one embodiment, a drag reducing device 10 is mounted to therear of a trailer T, as depicted in FIGS. 1-7. In particular, the device10 is mounted between the side wall S of the trailer and a rear door D.The rear door D can be of a typical configuration to rotate outwardabout a hinge H, as shown in FIG. 3. As also shown in those figures, thedrag reducing device remains attached to the side wall S and rear door Das the door is pivoted from its closed position, depicted in FIG. 7, toits open position, illustrated in FIG. 6. The device 10 includes a pairof mounting components for attaching the device to the vehicle,including a rear plate 12 and a side plate 14 connected by an airturning component 16. Each of the plates 12, 14 and air turningcomponent 16 are elongated to be at least nearly co-extensive with theheight of the rear door D, as best seen in FIG. 1. Optimally, the device10 extends along the entire height of the trailer body T.

The rear plate 12 mounting component is attached to the rear door D by ahinge 20. Likewise, the side plate 14 mounting component is attached tothe side wall S of the trailer T by a hinge 26. In one embodiment, thehinges 20, 26 may extend along the entire length of the plates, such asa piano hinge. However, other hinge arrangements are contemplated thatpermit a suitable range of rotation, such as a series of hinges, a kederor other suitable hinge configurations. For instance, as seen bycomparing FIGS. 6 and 7, the hinge 26 attached to the trailer side wallS is configured so that the side plate 14 can pivot almost 180° betweenthe actuated or deployed position of the device (FIG. 6) and the stowedposition (FIG. 7). Similarly, the hinge 20 connecting the rear plate 12to the door D pivots through about 120° from the deployed position tothe stowed position.

The air turning component 16 is connected to the two plates byrespective hinges 22, 24. The angular range of relative movement at thehinges 22, 24 is not as great as for the hinges 20, 26. In oneembodiment, the hinge 22 between the rear plate 12 and the air turningcomponent 16 is a piano hinge. The hinge 24 between the air turningcomponent and the side plate 14 may have a different configuration, asshown in detail in FIGS. 4-5. In this embodiment, the hinge 24 is aninterlocking pivoting arrangement that includes an elongated channel 30defined on the side plate 14 and a mating elongated bead 32 defined onthe air turning component 16. The bead 32 is configured to slide intothe channel 30 in a close running fit. The air turning componentincludes a flange 34 that projects toward the side plate 14 and contactsa rib 36 on the side plate to limit the relative rotation of the airturning component 16 toward the side plate 14. In particular, as shownin FIG. 7, the flange 34 contacts the rib 36 when the device 10 isdeployed. As the device moves to its stowed position remains in contactfor part of the movement, as shown in FIG. 3, but then moves out ofcontact with the rib is the door is pivoted further, as reflected inFIGS. 5 and 6. The flange 34 may contact the rear door D when the deviceis fully stowed (i.e., the door is fully open), as shown in FIG. 6. Thehinges 22, 24 are configured to allow the device 10 to fold to as smalla width as possible, limited only by the width of the air turningcomponent 16. In a preferred embodiment, the air turning component 16 isconfigured to a width W (FIG. 6) of 2-4 inches, which allows the reardoor D to be fully opened in accordance with typical usage of thetrailer T.

As shown in FIG. 7, the air turning component 16 defines a smootharcuate surface 17 from the side wall S of the trailer to the rear ofthe trailer. The component is configured to “turn” the air flow Fthrough an angle α that reduces the turbulence and prevents flowseparation at the rear of the trailer. It has been found that “turning”the air flow F in this manner reduces the pressure drag as the vehiclemoves through the air. In one embodiment, the air turning component 16is configured to produce an angle α of greater than 10°. In certainembodiments the component 16 is configured to produce an angle α ofabout 30°, which is believed to provide an optimum drag reducing effect.The outer surface 17 of the component 16 is thus configured at a radius,which in certain embodiments may be greater than 2.0 in. and less than6.0 in. In one specific embodiment the outer surface is defined at aradius of about 4.0 in. to provide a balance between the air flowturning angle and the profile or prominence of the device.

It is further contemplated that the side plate 14 may be arranged at anangle β relative to the side S of the truck/trailer. This angle mergesinto the air turning component to provide for a smooth transition of theairflow from along the side of the vehicle to the turning component 16.The angled side plate also allows the device to fit around trailerappurtenances, such as the door hinges. It is believed that thistransition helps collimate the air flow which in turn reduces the riskof flow separation or turbulence at the air turning component. In oneembodiment the angle β is no greater than about 5°. It can beappreciated that the flange 34 may be arranged to abut the side wall Swhen the device 10 is in its active deployed position. The overall widthof the hinge 24, or more specifically the height of the rib 36, may thusbe adjusted to determine the angle β.

The air turning component 16 may be formed as an extrusion of a durablematerial, such as aluminum or stainless steel, or extruded or moldedfrom a durable plastic, such as ABS plastic. The extrusion mayincorporate a generally hollow interior frame 16 a (FIG. 5) inside theinner surface of the component that helps the component resist crushingin the stowed position or resist impacts when in the deployed position.The frame 16 a may also be configured to house other components toassist in the drag reducing function of the device 10. For instance, ifthe device incorporates certain active device components, such as plasmaactuators and vehicle lights, the components may be housed within theinterior frame 16 a.

It can be appreciated from the sequence depicted in FIGS. 1-7 that thedevice 10 can be deployed and stowed without any intervention by thevehicle operator. The device 10 moves with the rear door D so that whenthe door is closed, as shown in FIG. 7, the device is automaticallysituated in its deployed or actuated position. When the door is opened,as shown in FIG. 6, the device 10 automatically moves to its stowedposition. The air turning component 16 is the primary functionalcomponent of the device since it is the curvature of the surface 17 thatturns the airflow at the rear of the vehicle. The device 10 isconfigured so that the air turning component 16 is supported by theplates 12, 14 in all positions of the device. The air turning component16 is large enough to present a sufficient surface to effectively turnthe air flow, but is small enough in width W so that the device 10 doesnot interfere with the normal opening of the rear doors D of thetrailer.

It can be appreciated that the side plate 14 of the device provides asmooth, seamless transition from the side wall S of the trailer to theair turning component 16. The hinge arrangement 24 between the side walland the air turning component allows for an uninterrupted surface fromthe surface of the side plate to the outer surface 17 of the air turningcomponent. The hinges 20, 22, 24 and 26 can be configured so that whenthe device 10 is deployed (FIG. 7) the hinge 24 is tightly closed sothat only a negligible seam exists at the interface between the sideplate and air turning component.

In an alternative embodiment, the plate 12 may be replaced with aretraction element, such as the retraction element 40 of the dragreducing device 10′ illustrated in FIGS. 8-10. The device 10′ includes aside plate 14 mounted to the side S of the truck or trailer by a hinge26. The side plate 14 it connected to the air turning component 16′ by ahinge 24. The hinges 24, 26 and side plate 14 of the device 10′ in FIG.8 may be constructed as like components of the device 10 in FIG. 3.Unlike the device of FIG. 3, the device 10′ uses a number of retractionelements 40 as a mounting component in lieu of the rear plate 12. Eachretraction element 40 is configured to exert an elastic force on the airturning component 16′ to hold the component in its deployed position, asshown in FIGS. 8-9. In one embodiment, each retraction element includesa resilient elastic band or strap 41 connected at one end to a rear doorD and at an opposite end to the air turning component 16′. The ends ofthe elastic strap 41 may include fittings 43, 45 adapted to engage hooks42, 44. The hook 42 are further connected to a fitting 22′ on the airturning component 16′, while the hook 44 is connected to a fitting 46mounted to the rear door D. It is contemplated that multiple retractionelements 40 are engaged between the device 10′ and the rear door atspaced apart positions. Preferably, at least three such retractionelements are used.

The retraction elements 40 act in a manner similar to the rear plate 12of the previous embodiment. When the device 10′ is in its deployedposition, as shown in FIG. 9, the retraction elements apply a force topull the air turning component 16′ toward the rear door. The elasticforce of the band 41 is resisted by the contact between flange 34 andrib 36 which prevents further rotation of the air turning component 16′toward the door. When the door D is opened to the position shown in FIG.10, the retraction elements 40 keep the air turning component 16′ tightagainst the rear door.

The retraction elements 40 may be connected to the rear door D and airturning component 16′ using other types of connectors. The retractionelements may utilize other resilient and/or elastic elements, such assprings; however, the elastic bands 41 provide a unitary structure thatis better able to withstand road vibration and dirt. The elastic bandsare also easily replaced by simply removing the hooks 42, 44 from thecorresponding fittings 43, 45.

In an alternative embodiment shown in FIGS. 11-13, a drag reducingdevice 10″ includes an air turning component 16″ in the form of anelongated extrusion in which the outer surface 17″ follows the curvaturedescribed above to turn the air flow. The extruded turning component 16″is attached to a side plate 14″, and more particularly to an inwardflange 15″ of the plate. The side plate 14″ is connected at a hinge 26″to a mounting plate 27″ that is mounted to the side S of the vehicle.The hinge 26″ permits the full range of pivoting of the air turningcomponent and side plate from the deployed position of FIG. 12 to thestowed position of FIG. 13. The hinge 26″ may thus be constructed likethe hinges described above.

The mounting plate 27″ includes an outwardly projecting flange 28″against which the side plate 14″ bears when the device is deployed, asshown in FIGS. 11-12. This flange thus maintains the side plate at apredetermined angle relative to the side S of the vehicle to impart theangle β described above (see FIG. 7). The device 10″ incorporates aretraction element 40″ that serves as the mounting component connectedbetween the extrusion 16″ and the door D. The retraction elementincludes a lanyard or tether 41″ that is generally non-extensible,unlike the strap 41 described above. The lanyard if fastened at end 46″to the door D and at the opposite end 42″ to the extrusion 16″, such asby way of a machine screw or other similar fastener. As shown in FIG. 13the lanyard flexes or folds when the device 10″ is in its stowedposition. As with the other embodiments the device 10″ and particularlythe extrusion 16″ is configured so that only a minimal gap existsbetween the door D and side S of the vehicle.

In the embodiments of FIGS. 1-13, the devices 10, 10′ are continuouslyattached to both the rear door and side wall of the truck/trailer. In analternative embodiment the leading end of the device may bedisengageable from the trailer. Thus, as shown in FIGS. 14-16, a device50 may include a rear plate 52 that is attached to the rear door D by ahinge 56, in the same manner as described above for rear plate 12described above. The device 50 includes an air turning component 54 thatis connected by a hinge 58 to the rear plate 52 at its trailing edge.The component 54 is configured to produce the air turning effectsdescribed above and may have the same general configuration as theturning components 16, 16′. The component 54 may thus be configured sothat the outer surface 55 follows a radius of greater than about 3.0 in.to turn the air flow at the angle α of greater than 15°.

The leading edge of the air turning component 54 includes mountingcomponent in the form of a side plate having an attachment element 60that removably engages a socket 62 mounted to the hinge frame of therear door. The attachment element 60 may include cut-outs 61 alignedwith the hinges H of the rear door D to allow the attachment element tosit as flush to the side wall S of the trailer as possible. In oneembodiment, the attachment element may include a magnet 66 thatmagnetically adheres the attachment element 60 to the socket 62. Aflange 64 may be provided to engage the socket 62 to hold the device 50against accidental disengagement. In an alternative embodiment, themagnet 66 may be replaced with a push-in type barbed fastener 66′, asshown in FIG. 16. The socket 62′ may be configured so that the opening63′ engages the barbs of the fastener 66′ to prevent its inadvertentdislodgment.

It is understood that a plurality of attachment element and socketcombinations are provided along the length of air turning component 54.The magnets 66 may be permanent magnets that are sufficiently strong tohold the leading edge of the component 54 against the side wall S underthe typical maximum air speed passing along the side the vehicle.However, the magnetic engagement between the sockets and magnets mustnot be too strong that the device cannot be manually disengaged from thetrailer.

In this embodiment, the device 50 requires intervention to disengage theattachment element 60 from the socket 62. The device may incorporate aninternal frame 68, similar to the frame 16 a of FIG. 5, which helpsmaintain the integrity of the air turning component as it is grasped bythe vehicle operator to disengage all of the attachment elements 60 fromall of the sockets 62. As with the prior embodiments, the hinge 56allows the rear plate 52 to pivot so that it rests against the rear doorD when the door is fully opened. The hinge 58 between the component 54and rear plate 52 allows the component to pivot inward toward the rearplate when the device 50 is in its stowed position. The hinge 58 may bespring biased so that the component 54 automatically pivots inward whenthe device 50 is disengaged from the socket 62. It is contemplated thatthis embodiment may be used with a vehicle having a single door, ratherthan the two side-swing doors in the illustrated embodiment.

Another automatically deployed embodiment is depicted in FIGS. 17-19. Inthis embodiment, the drag reducing device 70 includes a rear component72 mounting component that is fastened to the rear door by a hinge 80,in a manner similar to the prior embodiments. A front plate 74 mountingcomponent is similarly attached to the side wall of the trailer by ahinge 86. An air turning component 76 is connected between the rearcomponent 72, by a hinge 82, and the front plate 76, via a hinge 84. Thedrag reducing device 70 may incorporate an interlocking hingearrangement or keder for both hinges 82 and 84. As shown in FIG. 17, thecomponent 76 is configured to turn the air flow at an angle α of greaterthan 15° in a manner similar to the above-described embodiments.

In this embodiment, the rear component 72 is not a rigid plate, as inthe prior embodiments, but a flexible plate. In the deployed position,the flexible rear component 72 bows outward away from the rear door, asshown in FIG. 17. When the rear door D is pivoted to its open position,the rear component 72 forms a slight bend 87 at the hinge 80, asillustrated in FIG. 18. The hinge 80 between the rear component 72 andthe air turning component 76 allows the rear component to bow slightlyat the interface to the air turning component. As the door continues topivot forward, the flexible rear component 72 forms a bowed portion 88adjacent the air turning component 76. The two bowed portions 87 and 88allow the flexible component to assume a thin profile when the rear doorD is fully opened, as depicted in FIG. 19.

As with the device 10, the drag reducing device 70 does not require anyoperator intervention to deploy or stow. The natural stiffness of therear component 72 holds the air turning component 76 in its properposition. The hinge 86 for the front plate 74 may be spring biased tohold the front plate against the side wall of the trailer to assist inmaintaining the air turning component in its proper orientation.

The drag reducing devices disclosed herein may be configured for use ona sliding cover system, such as the CONESTOGA® rolling tarp systemmanufactured and sold by Aero Industries, Inc. Thus, in one embodiment,a drag reducing device 120 is mounted to the rear frame structure B of asliding cover system SC, as depicted in FIGS. 20-22. A pair of suchdevices 120 are mounted to the rear frame structure B on each side of arear closure RC (which may be a curtain or roll-up door, for instance)and are held in their deployed positions by a tension element 122spanning the closure. As shown in FIGS. 21-22, the tension element maybe a strap that may be tightened by a ratchet element 123 mounted by abracket 128 to an inner surface 127 of the device 120.

The device 120 may be in the form of a continuous extrusion, as depictedin FIG. 21. The extrusion defines a curved air turning surface 125 thatis configured similar to the outer surface 17 of the air turningcomponent 16 described above. In particular, the surface 125 may beconfigured to provide a smooth curved surface to turn the air flow by anangle of greater than 10° and in a specific embodiment about 30°. Thedevice 120 is mounted to the rear frame structure B by a pivot mount 126that may take on a variety of forms, such as a piano hinge, a sleeve andpintle, an interlocking rod and channel configuration or a keder. Sincethere is no outwardly swinging rear door, as in the prior embodiments,there is no special need for the device 120 to pivot fully against thesliding cover SC. Where the rear closure RC is a curtain, the device mayincorporate a rear curtain clamp 129 extending from the inner surface127 and arranged to pinch the rear curtain against the rear framestructure B when the device is in its deployed position. The rearcurtain clamp also reacts the tension applied by the tensioning element122 when the tensioning element is connected to the devices at oppositesides of the rear closure RC.

In an alternative embodiment, the tensioning element is replaced by alatch mechanism, such as the mechanism 132 included in the drag reducingdevice 130 shown in FIGS. 23-26. The drag reducing device 130 may beconfigured like the device 120 with a pivot mount 130 a (FIG. 26) to thetrailer rear frame structure B, a stiffening bracket 130 b and an airturning surface 130 c as described above. The latch mechanism 132includes a latch rod 136 that is slidably supported by upper and lowerbrackets 134 and 135, respectively, mounted to the inner surface 131 ofthe device. The rod 136 is mounted to slide upward into engagement witha latch plate 140 fastened to the rear frame structure B, as shown inFIG. 23, and downward to disengage the latch plate, as shown in FIG. 25.

The latch rod is moved upward by a cam lever 137 that is mounted to theinner surface 131 at a pivot mount 138. The lever includes a cam surface139 that contacts the latch rod 136 and is configured to move the rodupward upon rotation of the lever from the vertical orientation shown inFIG. 24 to the horizontal orientation shown in FIG. 26. A stop 140prevents over-rotation of the cam lever 137, holding the lever in itsvertical orientation to keep the lever within the envelope of the dragreducing device 130. The cam lever is manually operated to unlatch thedevice 130 from the rear frame structure B so that the device can bepivoted clear of the rear closure.

FIG. 27 depicts an alternative locking mechanism 150 for use with theside drag reducing device 130′, similar to the device shown in FIGS.21-26. In this embodiment the extrusion forming the device 130′ ismodified to include a cut-out 130 d with a back wall 130 e at the bottomof the device, as shown in FIGS. 27-29. The locking mechanism 150includes a thumbwheel actuator 151 that is used to move a pressure plate152 into engagement with a receiver plate 154 fastened to the back wall130 e of the device 130′, as shown in FIG. 27. The receiver plate 154may incorporate a recess within which the pressure plate 152 is seatedwhen the pressure plate is clamped onto the receiver plate. Thethumbwheel actuator is supported by a mounting block 153 carried by apivoting bracket 155. The thumbwheel actuator 151 and mounting block 153are configured so that manual operation of the actuator 151 firmlyclamps the pressure plate 152 onto the receiver plate 154. Thus, athreaded interface may be provided in which the thumbwheel actuator isrotated to engage and release the pressure plate 152. Other interfacesare contemplated including a spring-biased interface that biases thepressure plate to the clamped position shown in FIG. 27. In thisspecific embodiment the thumbwheel actuator would be manually retractedto release the pressure plate from the receiver plate.

The locking mechanism 150 is pivotably mounted to the rear framestructure B so that the mechanism can pivot from the locked position inFIG. 27, to the intermediate position of FIG. 28, to the unlockedposition depicted in FIG. 29. In one specific embodiment, the pivotingbracket 155 is attached to the rear frame structure B by a pivot mount156 that may take on a variety of forms that allow the range of pivotingmotion depicted in the figures. It can be appreciated that when thelocking mechanism 150 is in its unlocked position of FIG. 29 the dragreducing device 130′ may be pivoted outward away to the side of the rearframe structure to allow access to the rear closure RC (FIG. 21).

A side drag reducing device 160 is shown in FIGS. 30-31 for use with asliding cover system, such as the system discussed above. The deviceincludes an extruded body 161 having a curved outer surface 162 thatincludes a portion 162 a that is curved to produce the air turningfeature described herein. The outer surface may further incorporate agenerally linear portion 162 b as also discussed above. The extrusion isfastened to the rear frame structure B of the sliding cover system byway of a hinge 170. The hinge 170 is configured so that the device 160may pivot from the deployed position shown in FIG. 30 to the stowedposition shown in FIG. 31. The extruded body 161 may further include aninner wall 164 and a rear wall 165. The rear wall may support a receiverplate 154 to incorporate the locking mechanism 150 described above.

In one feature of the device 160, the inner wall 164 projects toward acurtain clamping base CB of the cover system in which the rear closureRC is a curtain. As shown in FIG. 31, the rear curtain includes a sidebead E on each side of the curtain that is aligned with the clampingbase CB. The side bead adds some rigidity to the rear curtain andfacilitates closing the curtain. For instance, in certain flexible coversystems, such as the CONESTOGA® cover system manufactured by AeroIndustries, Inc., the side bead E is engaged by a rear curtain hingedclamp that may be mounted to the hinge 170. The hinged clamp compressesthe side bead E into the clamping base to engage and seal the rearcurtain to the rear frame structure B. In accordance with the presentembodiment of the side drag reducing device 160, the inner wall 164terminates in an end plate 167 that extends the length of the extrudedbody 161, which in turn extends for substantially the entire length ofthe rear curtain. The inner wall 167 acts as a rear curtain clamp tocompress the side bead E into the clamping base CB as shown in FIG. 30.With this feature the drag reducing device 160 can replace the curtainhinged clamp with no modification to the rear frame structure.

The air turning aspect can also be implemented at the top rear edge ofthe trailer, or more particularly generally contiguous with the rearedge of the roof of the vehicle/trailer. As depicted in FIG. 1, an upperdrag reducing device 200 may be provided that can be deployed and stowedwithout interfering with the ability to fully open the rear doors. Apair of devices may be mounted to the rear doors D, leaving a gap G asneeded to accommodate rear lights of the trailer or vehicle. The device200 may be include an extrusion 201, as shown in FIGS. 32-34, thatextends along half the width of the trailer T (when two separate devicesare used), or that extends across the entire width of the trailer (whena single device is used). The extrusion 201 includes a leading surface202 and a trailing surface 204, in which the leading surface may becurved in the same manner as the side-mounted device, such as device 10discussed above. Thus the curvature of the leading surface is configuredto turn the airflow through an angle of at least 10° and in a specificembodiment by about 30°. The trailing surface 204 may emulate thesurface 162 of the side mounted device shown in FIG. 30 to reduceturbulence as the airflow leaves the leading surface 202. A downwardflange 206 may project from the front edge of the leading surface 202.The flange may be configured to abut the rear of the roof R of thetrailer, or may be configured to seat within a channel or trough in theroof. Engagement between the flange 206 and the roof of the vehiclemaintains the leading surface generally contiguous with the roof andensures a smooth airflow transition from the roof to the drag reducingdevice 200.

The extrusion 201 includes a bottom wall 210 that is hingedly connectedto the vehicle door D. A stiffening rib 208 may be provided between thebottom wall and upper surface. The rib further defines a generallyenclosed compartment 209 that can may house various components, such asa plasma actuator operable to generate a plasma airflow across the upperdrag reducing device 200. In one embodiment a hinge 212 is provided thatallows the extrusion 201 to pivot forward relative to the door D whenthe door is opened and the device is in its stowed position shown inFIGS. 33-34. The hinge may be configured to limit the rearward movementof the device 200 away from the door so that the flange 206 always abutsthe trailer when in the deployed position. When the rear door D isopened, the trailing surface 204 contacts the side wall S of thetrailer, which caused the extrusion 201 to pivot about the hinge 212over the top edge of the door, as shown in FIG. 33. This feature allowsthe top drag reducing device 200 to pivot clear of the space between thedoor D and trailer side S so that the door can be fully opened, as bestshown in FIG. 31.

A retraction element 220 may be provided that restores the drag reducingdevice 200 to its operative position when the door D is moved from theopen position of FIGS. 33-34 to the closed position shown in FIG. 29. Inone embodiment the retraction element may be similar to the retractionelement 40 shown in FIG. 8, in particular including an elastic band 221,connected by hooks 223, 225 to the vehicle door D and extrusion 201,respectively.

In certain embodiments the device 200 may be configured to extend acrossthe entire width of both rear doors D, rather than including the gap Gshown in FIG. 1. It can be appreciated that the gap G corresponds to thelocation of the upper rear lights for the trailer. In embodiments wherethe device extends uninterrupted across the width of the trailer theextrusion 201 may be formed of a generally transparent material so thatthe vehicle lights are visible through the extrusion. Thus, theextrusion may be formed of a polycarbonate resin thermoplastic, or othertransparent and durable plastic or polymer material. In otherembodiments the length and angle of the trailing surface 204 may bemodified so that it does not visually interfere with the rear trailerlights.

Alternatively, the extrusion 201′ of the device 200′ may be modified toinclude a notch 230 formed in the trailing surface 204′, as shown inFIG. 35. The notch is aligned with the lights on the rear of the traileror on the rear doors D so that the light are visible when the device200′ is deployed. The notch need only be defined in the underside of theextrusion 201′ since the lights will be viewed from below the level ofthe device 200′ mounted on the truck/trailer.

A top drag reducing device 250 is shown in FIGS. 36-38 that is supportedon the rear door D by angled struts 260. The device 250 includes an airflow turning component 251 in the form of an extrusion that forms aleading surface 252 and a trailing surface 254. The leading and trailingsurfaces can be configured like the leading and trailing surfacesdescribed above to turn the air flow in the manner also described above.The leading edge 253 is configured to abut the rear of the trailer toprovide a smooth air flow transition from the over the roof of thetrailer to the drag reducing device 250.

The extrusion 251 further includes a support plate 256 that may includea pair of C-shaped channels 257, 258 running along the length of theextrusion. The channels 257, 258 may be configured to receive a slidingfastener, such as a fastener for attaching the angled struts 260 to theextrusion. In another embodiment the angled struts are attached directlyto the support plate 256, such as by welding or a mechanical fastener.The angled struts are mounted to the rear door D by a corresponding pairof hinges 262. The hinges are configured to be closed when the device250 is in its deployed position, as shown in FIG. 36. The hinges areopened when the door is opened, as shown in FIG. 38, so the device 250can pivot over the top of the door so as not to impede movement of thedoor to the fully opened position. The hinges are preferably springbiased to bias the struts to the deployed position of FIG. 36 in orderto maintain the leading edge 253 in tight contact with the rear of thetrailer.

The leading edge 253 of the leading surface 252 may abut a generallyplanar gutter foil 270 (FIGS. 36-37) that is mounted to the rear of theroof R of the trailer. The gutter foil 270 is configured to sit over oneor more rear gutters of the trailer, extending forward from the rear tospan a desired number of gutters. The gutter foil reduces the airflowturbulence produced as the air passes over the disruptions in the roofsurface created by the gutters. Since the gutters do not span the entirewidth of the trailer, as seen in FIG. 37, the function of the gutters isnot impaired. Moreover, the gutters may be perforated to permit waterflow into the gutters. In certain embodiments the leading surface 252 ofthe device may be modified to incorporate the gutter foil. In thismodification, the leading surface would extend forward over gutters whenthe device is deployed.

A modified extrusion 280 for a top drag reducing device is shown in FIG.39 which is configured for use alternatively in a panel trailerconfiguration, like the device 250, or with a sliding cover system. Theextrusion includes a leading surface 281, a turning surface 283 and atrailing surface 284. The turning and trailing surface may be configuredas described above to turn the air flow and prevent turbulence. Theleading surface 281 may include a generally planar portion 282 providedto extend the airflow turning effect farther to the rear of the vehicleso that the leading surface can help collimate the airflow exiting theroof of the trailer or sliding cover system. The leading surface 281 maythus act as the gutter foil 270 discussed above.

The extrusion includes a support plate 287 with a pair of C-shapedchannels 288, 289 for mounting components or support struts thereto. Theextrusion further includes a rear panel 290 that may be configured toabut the rear of the trailer or rear frame structure. The rear panel mayinclude a C-shaped channel 291 that is configured to receive a bead E ofa rear curtain closure RC. The rear panel 290 may further include arecess 292 for mounting the device directly to the upper portion of arear frame structure. When the device 280 is used with a sliding coversystem, the extrusion is fastened to the rear frame structure B via therecess 292 using conventional fasteners. A rear curtain closure RC maybe carried by the device by mounting the top bead E within the channel291. In this instance the C-shaped channels 288, 289 are not used.

Some vehicles/trailers utilize a roll-up rear door, such as the trailerT and rear door RD depicted in FIG. 40. In one embodiment, side dragreducing devices 300 and a top drag reducing device 320 are mounted tothe rear frame of the vehicle. As best seen in FIGS. 41-42, the devices300, 320 are modified from the device 280 shown in FIG. 39. Inparticular, the devices 300, 320 do not include the planar portion 282or the rear panel 290. On the other hand, the devices 300, 320 doinclude a turning surface 303, 323, and a trailing surface 304, 324, aswell as the channels 305, 325 projecting from a support plate 307, 327.The devices are mounted by hinges 302, 322 to the respective sides andtop of the rear frame supporting the roll-up rear door RD. The hingesmay be spring-biased to bias the respective drag reducing device toeither the deployed or stowed position. In one embodiment, the hinges302, 322 are spring biased to bias the devices to the stowed positionsdepicted in FIG. 41.

In one aspect, the drag reducing devices are held in their deployedposition shown in FIG. 42 by cables or cords 330. In one specificembodiment the cables 330 are bungee cords or other elastic cable toprovide a restraining force sufficient to hold the drag reducing devicesin their deployed position in spite of road shock and vibrations. Asdepicted in FIG. 40, the cables 300 are mounted cross-wise between thetop drag reducing device 320 and each side drag reducing device 300. Thecables may be specifically mounted within the channels 305, 325 of thedevices using appropriate fasteners. In an alternative approach, a setof cables may be connected between the top drag reducing device 320 andthe base of the rear frame of the vehicle and another set of cables canbe connected directly between the two side drag reducing devices(similar to the strap 122 shown in FIG. 20)

In each of the top drag reducing devices described above it can beappreciated that the devices provide drag reduction features withoutprojecting appreciably above the roof R of the vehicle/trailer. Vehiclesof this type are subject to height restrictions. In many cases, thevehicle/trailer is manufactured to maximize the enclosed volume tothereby maximize the amount of load that can be transported. Thus,vehicle/trailer manufacturers make the vehicles/trailers as tall aspossible, or more specifically as close to the legal height limits aspossible. Since the height restrictions apply to anything mounted to thevehicle/trailer, most prior top drag reducing devices mounted to theroof R cause the vehicle to exceed the height limits. The top dragreducing devices 200, 250, 280 and 320 disclosed herein are essentiallyflush with the surface of the roof R and in some cases, lower than thegutter structure of some vehicles/trailers.

In all the embodiments the drag reducing device includes a contoured orcurved surface that is configured to turn the airflow passing the rearof the trailer or vehicle. In preferred embodiments the surface turnsthe airflow at least 10°, and in a specific embodiment about 30°, as theair flows past the drag reducing devices. This modified airflow reducesturbulence at the rear of the vehicle and thus reduces drag. It isfurther contemplated that the trailing end of the air flow turningcomponents may incorporate a generally straight section followed by anadditional curved section to turn the air flow further toward the rearof the vehicle. The additional curved section may be calibrated inconjunction with the first curved section to turn the air flow tooptimize the drag reduction performance of the device. The drag reducingdevices disclosed herein may incorporate an extruded air turningcomponent that can also be used to house additional drag reducingcomponents, such as plasma actuators. For these modified devices thecurved surface may be defined at a different radius than discussedabove. In particular, the addition of certain plasma actuators canachieve the desired airflow turning angle with a curved surface having aradius less than 3.0 inches, and in a specific embodiment a radius of2.0 inches.

In each of the embodiments an extrusion is provided as the air turningcomponent. The extrusion allows tailoring the device to the size of theparticular truck/trailer. Thus, the side drag reducing devices may becut to match the height of a particular vehicle, while the top dragreducing devices may be cut to the width of the vehicle. In many casesit is desirable for the drag reducing devices to be as long as thevehicle permits in order to maximize the drag reducing performance.

What is claimed is:
 1. A drag reducing device for a vehicle, the vehiclehaving opposite side walls, a rear perimeter with a rear opening and atleast one door at the opening, said device comprising: an air flowturning component, associated with each of the vehicle side walls,having a curved surface adapted to turn air flow passing over saidcurved surface when in a deployed position; a first mounting componentfor connecting the air flow turning component to the door; and a secondmounting component for connecting the air flow turning component to acorresponding one of the opposite side walls, wherein said first andsecond mounting components support said air flow turning componentextending rearward from the vehicle side walls in said deployedposition.
 2. The drag reducing device of claim 1, wherein said curvedsurface is defined at a curvature configured to turn the air flowpassing the vehicle side wall toward the rear of the vehicle by at least10°.
 3. The drag reducing device of claim 2, wherein said air turningcomponent further includes a trailing surface integral with a rearportion of said curved surface, said trailing surface being generallyplanar.
 4. The drag reducing device of claim 1, wherein said curvedsurface is defined at a radius of at least 2.0 inches.
 5. The dragreducing device of claim 4, wherein said curved surface is defined at aradius of between 3.0 and 6.0 inches.
 6. The drag reducing device ofclaim 5, wherein said curved surface is defined at a radius of about 4.0inches.
 7. The drag reducing device of claim 1, wherein said air turningcomponent is an elongated extrusion having a length nearly equal to theheight of the door of the vehicle.
 8. The drag reducing device of claim1, wherein: said first mounting component includes a rear plate hingedlyattached at one side to said air flow turning component and hingedlyattached at an opposite side to the door; and said second componentincludes a side plate hingedly attached at one side to said air flowturning component and hingedly attached at an opposite side to thevehicle side wall.
 9. The drag reducing device of claim 8, wherein saidrear and side plates are hingedly attached to said air turning componentand to the door and side wall, respectively, by corresponding hinges,said hinges configured so that said air turning component can move fromsaid deployed position aligned with the side wall of the vehicle to astowed position between the door and the side wall when the door isfully opened.
 10. The drag reducing device of claim 9, wherein the hingebetween said side plate and the vehicle side wall is configured to allowthe side plate to pivot through about 180°.
 11. The drag reducing deviceof claim 9, wherein the hinge between said side plate and said airturning component is arranged between the vehicle side wall and saidside plate to offset said side plate away from the vehicle side wall atan angle relative thereto when said device is in said deployed position.12. The drag reducing device of claim 11, wherein said hinge betweensaid side plate and said air turning component includes a rib projectingfrom said side plate toward the vehicle side wall in said deployedposition and a generally planar flange extending from said air turningcomponent to contact said rib in said deployed position.
 13. The dragreducing device of claim 12, wherein said rib is sized so that said ribholds said planar flange against the vehicle side wall in said deployedposition.
 14. The drag reducing device of claim 11, wherein the hingebetween said rear plate and said air turning component is configured sothat said rear plate is disposed between said air turning component andthe rear door when rear door is fully opened and said air turningcomponent is in said stowed position.
 15. The drag reducing device ofclaim 1, wherein said first mounting component includes at least oneelongated elastic strap attached at one end to said air turningcomponent and at an opposite end to the rear door.
 16. The drag reducingdevice of claim 1, wherein said first mounting component includes atleast one elongated lanyard attached at one end to said air turningcomponent and at an opposite end to the rear door.
 17. The drag reducingdevice of claim 1, wherein said second mounting component includes anattachment element configured to be removably attached to the vehicleside wall.
 18. The drag reducing device of claim 17, wherein said secondmounting component includes a side plate extending from said attachmentelement to said air turning component, said side plate defining cutoutsfor receiving the hinges of the vehicle rear door.
 19. The drag reducingdevice of claim 17, wherein said second mounting component includes asocket defined in the vehicle side wall and said attachment element isconfigured for removable engagement within said socket.
 20. The dragreducing device of claim 19, wherein said attachment element includes amagnet.
 21. The drag reducing device of claim 19, wherein saidattachment element includes a barbed fastener configured for push-inengagement within said socket.
 22. The drag reducing device of claim 1,wherein said first mounting component includes a flexible plate attachedat one side to said air turning component and hingedly attached at anopposite side to the rear door, said flexible plate adapted to at leastpartially fold onto itself when the rear door is fully opened and saidair turning component is in its stowed position.
 23. The drag reducingdevice of claim 1, wherein said air flow turning component includes ahollow frame defined on an interior face of said curved surface.
 24. Thedrag reducing device of claim 23, further comprising one or moreelectrical accessories mounted within said hollow frame.
 25. A dragreducing device for a vehicle having a sliding cover system and a rearframe structure having a rear perimeter defining a rear opening with arear closure extendable to cover the rear opening, said devicecomprising: a pair of air flow turning components, one on each side ofthe rear frame structure and each having a curved surface adapted toturn air flow passing over said curved surface; a pivot mount betweenthe rear frame structure and each of said pair of airflow turningcomponents, each pivot mount configured to pivot the component from adeployed position in which said curved surface is aligned with the sideof the rear frame structure to turn air flow passing from the side wallof the rear frame structure to a stowed position outboard of the rearframe structure; and a locking element associated with each of said pairof air flow turning components configured to lock the components in saiddeployed position.
 26. The drag reducing device of claim 25, whereinsaid locking element includes a tension element spanning the width ofthe rear frame structure and releasably connected between said pair ofair flow turning components in said deployed position.
 27. The dragreducing device of claim 25, wherein said locking element includes: alocking bar slidably mounted to each of said pair of air turningcomponents, said locking bar configured to engage a portion of the rearframe structure to prevent pivoting of the air turning component; and amanual lever pivotably mounted to each of said pair of air turningcomponents and arranged to move said locking bar to and from engagementwith the rear frame structure upon pivoting of said lever.
 28. The dragreducing device of claim 25, wherein said locking element includes: areceiver plate attached to lower end of said airflow turning componentand facing rearward when said airflow turning component is in saiddeployed position; an actuator having a pressure plate, said actuatorconfigured to press said pressure plate against said receiver plate in alocked position and to release said pressure plate therefrom in anunlocked position; and a bracket pivotably mounted to the rear framestructure and supporting said actuator, said bracket configured to pivotsaid actuator to and from a position in which said pressure plate isaligned with said receiver plate.
 29. The drag reducing device of claim28, wherein said actuator includes a thumbwheel actuator threadedlyengaged to said bracket so that rotation of said thumbwheel actuatormoves said pressure plate toward and away from said receiver plate. 30.The drag reducing device of claim 25, wherein said curved surface isdefined at a curvature configured to turn the air flow passing thevehicle side wall toward the rear of the vehicle by at least 10°. 31.The drag reducing device of claim 30, wherein said air turning componentfurther includes a trailing surface integral with a rear portion of saidcurved surface, said trailing surface being generally planar.
 32. Thedrag reducing device of claim 25, wherein said curved surface is definedat a radius of at least 2.0 inches.
 33. The drag reducing device ofclaim 32, wherein said curved surface is defined at a radius of between3.0 and 6.0 inches.
 34. The drag reducing device of claim 33, whereinsaid curved surface is defined at a radius of about 4.0 inches.
 35. Thedrag reducing device of claim 25, wherein each air turning component isan elongated extrusion having a length nearly equal to the height of therear closure.
 36. The drag reducing device of claim 25, in which therear closure is a flexible curtain that includes a side bead and therear frame structure includes a clamping base at each side for receivingthe curtain side bead, wherein each of said air flow components includesan inner wall extending from said curved surface toward the rear framestructure when said airflow turning components are in said deployedposition, said inner wall including a rear plate arranged to compressthe rear curtain side bead into the clamping base in said deployedposition.
 37. A drag reducing device for a vehicle, the vehicle having aroof and a rear perimeter with a rear opening and at least one door atthe opening, said device comprising: an air flow turning componenthaving a curved surface adapted to turn air flow passing over saidcurved surface when in a deployed position; a mounting component forconnecting the air flow turning component to the door, said mountingcomponent configured so that said curved surface is generally contiguouswith the vehicle roof in said deployed position.
 38. The drag reducingdevice of claim 37, wherein said mounting component includes a hingeconfigured to pivot said air flow turning component relative to the atleast one door to a stowed position extending over the door.
 39. Thedrag reducing device of claim 37, wherein said air flow turningcomponent is an extrusion defining said curved surface, and saidmounting component includes at least one elongated bracket attached atone end to said extrusion and at an opposite end to the at least onedoor.
 40. The drag reducing device of claim 37, wherein said curvedsurface is defined at a curvature configured to turn the air flowpassing the vehicle roof toward the rear of the vehicle by at least 10°.41. The drag reducing device of claim 40, wherein said air turningcomponent further includes a trailing surface integral with a rearportion of said curved surface, said trailing surface being generallyplanar.
 42. The drag reducing device of claim 37, wherein said curvedsurface is defined at a radius of at least 2.0 inches.
 43. The dragreducing device of claim 42, wherein said curved surface is defined at aradius of between 3.0 and 6.0 inches.
 44. The drag reducing device ofclaim 43, wherein said curved surface is defined at a radius of about4.0 inches.
 45. The drag reducing device of claim 37, wherein said airturning component is an elongated extrusion having a length nearly equalto the width of the door of the vehicle.
 46. The drag reducing device ofclaim 37, in which the vehicle roof includes at least one transversegutter adjacent the rear of the vehicle, wherein: said curved surfaceincludes a leading edge immediately adjacent the rear perimeter of thevehicle in said deployed position; and said air flow turning componentincludes a generally planar foil extending from said leading edge ofsaid curved surface and over the at least one gutter.
 47. The dragreducing device of claim 46, wherein said foil includes a number ofopenings aligned with the at least one gutter for passage of watertherethrough.
 48. The drag reducing device of claim 37, in which thevehicle includes lights on the rear perimeter adjacent the roof, whereinsaid air flow turning component includes a notch aligned with thevehicle lights for visibility of the lights when the component is in itsdeployed position.
 49. A drag reducing device for a vehicle, the vehiclehaving a roof and a rear perimeter with a rear opening and flexiblecurtain covering the opening, the curtain having a bead at the upperedge thereof, said device comprising an air flow turning componentincluding an elongated body sized to extend at least across the width ofthe flexible curtain, said body defining an upper curved surface adaptedto turn air flow passing over said curved surface, a rear wallconfigured to be mounted to the vehicle rear perimeter with said curvedsurface generally contiguous with the vehicle roof, and a transverselyextending elongated channel configured to receive the bead of thecurtain to support the curtain.
 50. A drag reducing device for avehicle, the vehicle having a roof and a rear perimeter with a rearopening and a roll-up door at the opening, said device comprising: a topair flow turning component having a curved surface adapted to turn airflow passing over said curved surface when in a deployed position; a topmounting component for hingedly mounting the top air flow turningcomponent to a top portion of the rear perimeter; said top mountingcomponent configured to move the top air flow turning component betweena deployed position in which the curved surface of the corresponding airflow turning component is generally contiguous with the vehicleperimeter in said deployed position, and a stowed position in which thetop air flow turning component is pivoted outward from the rearperimeter.
 51. The drag reducing device of claim 50, wherein said topmounting component includes a spring-biased hinge configured to bias thetop air flow turning component to the stowed position.
 52. The dragreducing device of claim 50, further comprising: a pair of side air flowturning components, each having a curved surface adapted to turn airflow passing over said curved surface when in a deployed position; and aside mounting component for hingedly mounting each of the side air flowturning components to opposite sides of the rear perimeter.
 53. The dragreducing device of claim 52, wherein said side mounting componentincludes a spring-biased hinge configured to bias the corresponding sideair flow turning component to the stowed position.
 54. The drag reducingdevice of claim 52, further comprising a number of cables connectedbetween said top air flow turning component and each of said side airflow turning components when the air flow turning components are intheir deployed position.
 55. A drag reducing device for a vehicle, thevehicle having a roof and a rear perimeter with a rear opening and aroll-up door at the opening, said device comprising: a pair of side airflow turning components, each having a curved surface adapted to turnair flow passing over said curved surface when in a deployed position; aside mounting component for hingedly mounting each of the side air flowturning components to opposite sides of the rear perimeter, said sidemounting component configured to move the corresponding side air flowturning component between a deployed position in which the curvedsurface of the corresponding air flow turning component is generallycontiguous with the vehicle perimeter in said deployed position, and astowed position in which the side air flow turning component is pivotedoutward from the rear perimeter.
 56. The drag reducing device of claim55, wherein said side mounting component includes a spring-biased hingeconfigured to bias the corresponding side air flow turning component tothe stowed position.